# Blood Pressure by MikeJenny

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‫‪BLOOD PRESSURE‬‬
WHAT IS BLOOD PRESSURE?

Blood pressure refers to the force (pressure) with which the blood presses
against the walls of the blood vessel. All blood vessels--large or small,
artery or vein--have blood pressure. However, the term blood pressure
normally refers to the blood pressure of a major artery. Unlike the other
vital signs discussed previously, it takes two numbers--the systolic
pressure and the diastolic pressure--to describe this vital sign. Blood
pressure is normally measured in millimeters of mercury (mm Hg).
"Millimeters of mercury" is a standard unit for measuring pressure. It refers
to how high a force (pressure) would cause a column of mercury (chemical
symbol Hg) to rise in a tube. Figure 5-1 gives the general idea. The greater
the pressure, the more mercury is forced up the tube.

Figure 1. "Millimeters of mercury" as a measure of pressure.

WHAT ARE SYSTOLIC AND DIASTOLIC PRESSURES?

Basically, the systolic pressure is the greatest pressure that the blood exerts
against the walls of the blood vessel while the diastolic is the lowest
pressure that the blood exerts against the walls of the vessel. A person's
blood pressure depends upon the force of the heart's pumping action, the
degree to which the blood vessel will stretch, and the amount of blood in
the blood vessel.
a. Systolic. The arteries are under the greatest pressure when the heart
pumps blood into them. The extra blood that is forced into the arteries
make them stretch.

(1) In a normal adult male, the systolic pressure should be between 100 and
140 mm Hg, inclusive. (Inclusive simply means to include the ends of the
range. Systolic pressures of 100 and of 140 are within normal range.)

(2) In a normal adult female, the systolic pressure should be between 90
and 130 mm Hg, inclusive.

b. Diastolic. The arteries are under the least pressure from the blood when
the heart is at rest (between pumps or beats) and the arteries have returned
to their normal size.

(1) In a normal adult male, the diastolic pressure should be between 60 and
90 mm Hg, inclusive.

(2) In a normal adult female, the diastolic pressure should be between 50
and 80 mm Hg, inclusive.

WHAT FACTS AFFECT A PERSON'S BLOOD PRESSURE?

There are several factors that can affect a patient's blood pressure. Some are
only temporary; others are long-term effects. A condition in which the
blood pressure is considerably above normal is called "hypertension." If the
blood pressure is too low, it is called "hypotension."

a. Condition of Cardiovascular System. A primary factor influencing a
patient's blood pressure is the condition of his cardiovascular system (heart
and blood vessels).

(1) If a patient's heart is not pumping blood with enough force, his blood
pressure will be low. This will decrease the rate that blood is circulated
throughout the body. Slow blood circulation may result in certain parts of
the body (especially the brain) not receiving enough oxygen since oxygen is
carried by the blood.
(2) If a patient's heart is pumping with too much force, his blood pressure
will be high. If an artery has a weak spot, the force of the systolic pressure
may be enough to rupture the artery and allow blood to escape.

(3) If a patient's arteries loose part of their elasticity, such as in patients
who have arteriosclerosis (hardening of the arteries), the patient's blood
pressure will be higher, since the artery walls stretch less and cannot
relieve as much pressure.

b. Age. A person's blood pressure readings tend to increase as he grows
older.

c. Gender. As indicated in paragraph 5-2, men tend to have higher blood
pressure than women of the same age.

d. Physical Fitness. People who are physically fit tend to have more normal
blood pressure than people who are "out of shape."

e. Obesity. People who are very overweight usually have higher blood
pressure than they would if their weight were closer to their ideal weight.

f. Pain. Pain is a type of body defense that lets the brain know that
something is wrong. The brain may respond to pain by increasing the rate
and strength of heartbeats. The increased rate increases the amount of
oxygen available to the muscles for producing energy. It also results in an
increased blood pressure.

g. Emotion. Fear, worry, excitement, and similar emotions can result in a
higher blood pressure. The brain may react to these emotions in basically
the same way that it reacts to pain.

h. Gravity. If a person is standing, the blood pressure of the arteries in the
lower part of the body will be greater than the pressure in the upper part of
the body.

i. Exercise. A person's blood pressure is greater during and just after
exercising because the heart beats faster in order to supply additional
oxygen to the muscles.
j. Disease. Almost any disorder that affects the arteries or the renal (kidney)
system will result in a higher blood pressure. Diseases that weaken the
heart will usually result in a lower blood pressure.

k. Drugs. Drugs designed to strengthen the actions of the heart, such as
digitalis, will cause the patient's blood pressure to rise. Drugs that cause
the arteries to become smaller in diameter (called vasoconstrictors) will
also cause the patient's blood pressure to rise. Drugs that cause the
patient's arteries to become larger in diameter (called vasodilators) will
decrease blood pressure.

l. Eating. A person's blood pressure is usually elevated (increased) while he
is eating and for a while after he finishes the meal.

m. Bleeding. Serious bleeding (hemorrhaging) reduces the amount of blood
in the body's circulatory system and thus reduces blood pressure.

WHAT EQUIPMENT IS NEEDED TO MEASURE A PATIENT'S
BLOOD PRESSU RE?
You will need a sphygmomanometer (sfig'-mo-mah-NOM-e-ter) and a
stethoscope (STETH-ah-skop).

Figure 5-2. Sphygmomanometers.

A Portable mercury sphygmomanometer.
B Portable aneroid sphygmomanometer.

a. Sphygmomanometer. The sphygmomanometer (figure 5-2) is usually
called the "blood pressure cuff." There are several different types of blood
pressure cuffs in use. Some are made to be attached to a wall (next to a
patient's hospital bed, for example), but most are portable. All blood
pressure cuff devices work basically in the same way and have the same
parts--a bladder, a handbulb with release valve, a tube connecting the
handbulb to the bladder, and a gauge (either mercury or aneroid) for
measuring pressure.

(1) Bladder. The bladder (also called the "cuff") is a long rubber bag about 6
inches wide and 24 inches long that is covered with fabric. The bladder is
wrapped around the patient's arm and filled with air when taking the
patient's blood pressure. Parts of the fabric are made of non-slip material,
such as Velcro. When the fabric is overlapped, the two pieces of fabric
adhere to each other and will not slip when the bladder is inflated. Some
sphygmomanometers use snaps or other devices to secure the bladder
instead of non-slip fabric.

(2) Handbulb. The handbulb is a device for inflating the bladder. When
squeezed, the handbulb forces the air through an opening connected to the
tubing. When the bulb is released, it refills with air from the environment.
The handbulb is designed so that air from the tubing cannot flow back into
the handbulb.

(3) Rubber tubes. One tube connects the bladder and handbulb. Air that is
forced out of the handbulb travels through the tube and enters the bladder.
A second tube connects the bladder and the gauge..

(4) Release valve. The release valve (screw) is a device for releasing air
from the bladder. It is located between the handbulb and the tubing. One
hand can operate both the handbulb and the release valve easily. The valve
is controlled by a screw. When tightened, no air escapes. When unscrewed
fully, the air escapes rapidly. (Note: The screw does not separate from the
apparatus. "Unscrewed fully" means the screw is turned so that air will
escape as fast as possible.) The screw can also be turned to any position
between completely closed and full release. In this way, you can let air
escape from the bladder as quickly or as slowly as you wish

(5) Gauge. The gauge measures the air pressure in the bladder. There are
two types of gauges--the mercury gauge and the aneroid gauge.

(a) Mercury. The mercury gauge has a column of mercury in a glass tube.
The column of mercury measures the air pressure in the bladder. The
higher the pressure of air in the bladder, the higher the column of mercury.
The height of the column of mercury is determined using a scale to the side
of the tube containing the mercury. Usually there is a scale on each side of
the glass tube in order to make it easier to read the height of the column.
As air is released from the bladder, the air pressure drops and the column
of mercury becomes shorter.

(b) Aneroid. The aneroid gauge is circular and has a dial. The greater the
air pressure in the bladder, the farther the needle on the dial rotates. A
scale on the dial is equivalent to the scale of the mercury gauge. Both scales
measure the force of air pressure in the bladder in terms of mm Hg. As the
air pressure is released, the needle moves in a counter-clockwise direction.
The gauge will normally be designed so that it can be attached to the
bladder. This frees the person taking the blood pressure from having to
hold the gauge in one of his hands.

b. Stethoscope. The stethoscope is an instrument used for listening to
sounds produced within the body. A stethoscope consists of a diaphragm,
metal and rubber tubing, and earpieces (figure 5-3).

(1) Diaphragm. The diaphragm is normally a flat metal disk that is placed
on the body area being examined. The diaphragm will pick up sounds
produced within the body such as the heartbeat and breathing sounds.
Sometimes a bell-shaped listening device is used instead of a flat disk.
Some stethoscopes have combination (both flat disk and bell) listening
devices.

(2) Tubing. The hollow and metal tubes transmit the sounds from the
diaphragm to the earpieces. The rubber tubing provides flexibility.

Figure 3. Stethoscope.

(3) Earpieces. The earpieces are twisted metal tubes with plastic ends. The
plastic pieces protect the ears from the metal. The twisting helps to
improve the quality of sound heard through the stethoscope. The
stethoscope should be worn with the earpieces forward (figure 5-4) to help
prevent the sounds picked up by the diaphragm from being distorted.

Figure 4. Earpiece of stethoscope in place for use.

HOW DOES THE AIR PRESSURE INSIDE THE BLADDER PROVIDE
INFORMATION ABOUT THE BLOOD PRESSURE?

Paragraph 5-1 stated that blood pressure is the force with which the blood
pushes against the walls of the blood vessel. However, paragraph 5-3a(5)
states that the gauge on the sphygmomanometer measures the air pressure

a. Indirect Measurement. Some things cannot be measured directly without
difficulty. For example, the height of a building can be measured by
climbing to the top of the building, holding on to one end of a very long
tape measure, and dropping the other end to a friend on the ground who
reads off the height. This method may work for a building that is not very
high, but is not recommended for determining the height of the Empire
State Building. The height of a building, however, can be determined
indirectly, such as by measuring its shadow. (Method: Put a stick in the
ground so that it is straight up and down. Measure the height of the stick,
the length of the stick's shadow, and the length of the building's shadow.
The height of the building is equal to the length of the building's shadow
times the height of the stick divided by the length of the stick's shadow.)

b. Blood Pressure Measurement. Just as the height of the building was
determined by measuring something else (its shadow), the pressure of the
blood at its highest (systolic) and normal (diastolic) levels can be
determined by measuring the air pressure in the bladder.

(1) When the bladder is first placed around the arm and not inflated, the
artery beneath the bladder functions normally (figure 5-5 A ).

(2) When the bladder is inflated, the bladder squeezes the arm. If the
bladder is inflated to a pressure greater than the systolic pressure of the
artery, the artery beneath the bladder will collapse (figure 5-5 B ). The
artery will remain collapsed, thus shutting off blood flow below the
bladder, even when there is a heartbeat. Thus, when there is no blood flow
in the artery below the bladder, you know that the air pressure in the
bladder is greater than the systolic blood pressure.

(3) When the bladder is inflated to a pressure that is less than the systolic
pressure but greater than the diastolic pressure, blood will flow beneath
the bladder only when the (blood) pressure within the artery is greater
than the (air) pressure within the bladder. This occurs when the force of the
heartbeat increases the pressure within the artery. Once the additional
force of the heartbeat has passed (the artery returns to diastolic pressure),
the artery will collapse again (figure 5-5 C ). Thus, when blood suddenly
passes through the artery beneath the bladder, stops, starts again, and
stops again, you know that the pressure within the bladder is less than the
systolic pressure but more than the diastolic pressure.

(4) If the bladder is inflated, but the pressure within the bladder is less than
the lowest level of pressure within the artery (diastolic pressure), then the
bladder cannot collapse the artery. The pressure of the bladder may
interfere somewhat with the blood flow, but it cannot stop the blood flow
(figure 5-5 D ). Thus, when the blood continues to flow through the artery
beneath the bladder without stopping, you know that the pressure within
the bladder is less than the lowest (diastolic) pressure of the blood within
the artery.
A Artery without the bladder--artery expands during heartbeat, returns to
normal.
B Air pressure in the bladder is greater than the systolic pressure--the
artery                          stays                            collapsed.
C Air pressure in bladder is between systolic pressure and diastolic
pressure--artery     collapsed        except       during        heartbeat.
D Air pressure in bladder is less than diastolic pressure--artery does not
collapse.

Figure 5. Effects of an inflated bladder on an artery.

HOW DO I TAKE A PATIENT'S BLOOD PRESSURE?
Use the following procedures when taking a patient's blood pressure.

a. Gather Materials. You will need the following items:

         Sphygmomanometer.
         Stethoscope.
         Cotton-tipped applicators (swabs)--at least 8.
         Disinfecti ng solution (70% alcohol solution).
         Watch or clock with second hand.
         Pen or pencil.
         Form or note pad on which to write.

b. Verify the Patient's Identity. Make sure that you are preparing to take
the blood pressure of the proper person.

c. Set up Equipment. If you have a portable mercury sphygmomanometer,
set up the gauge so that it will be at about eye level. If you are using an
aneroid gauge, position yourself or the patient so that the gauge will be
about eye level when you read it. You can read a gauge easier and more
accurately when it is at eye level.

d. Clean Earpieces. Wet one swap with the alcohol disinfecting solution.
Clean the inside of one plastic earpiece of the stethoscope with the swab
and discard the swab. Wet another swab, clean the outside of the plastic
earpiece, and discard that swab also. Repeat the procedure for the other
plastic earpiece.

e. Position the Patient. Have the patient to position himself in the desired
position.

(1) The blood pressure is normally taken using the patient's upper arm. The
patient can stand, sit, or lie down. Normally, the patient will sit with his
arm resting on a table or lie down with his arm resting on the bed, cot, or
ground.

(2) Sometimes, the physician orders that the patient's blood pressure be
taken on his thigh instead of on his arm. (The patient's arms may be injured
or amputated, for example.) If the blood pressure is to be taken using the
thigh, have the patient to lie on his abdomen. If the patient cannot lie on his
abdomen, have him to lie on his back with his knees flexed.

f. Expose the Site. Have the patient expose the site to be used (upper arm or
thigh). Assist the patient as needed. The patient may need to remove a long
sleeve shirt or lower his pajama bottoms. The bladder must be placed over
the patient's flesh, not his clothing. Rolling a shirt-sleeve or pants leg up
could create a tight area above the site where the bladder is applied. This
extra tightening could cause the blood pressure readings to be inaccurate.
Therefore, it is better to remove a long sleeve shirt or pants rather than
rolling them up.

g. Explain Procedure to Patient. Briefly tell the patient what you are going
to do. The explanation can be combined with instructing the patient to
expose the site where the bladder will be applied. Warn the patient that his
arm (leg) may be uncomfortable while the bag (bladder) around his arm
(leg) is inflated, but reassure the patient that the discomfort will only last 1
or 2 minutes.

h. Prepare Bladder. Make sure that the bladder is completely deflated. If air
is present in the bladder, open the release valve, force the air out of the
bladder, and close the valve.

i. Prepare Gauge. If a mercury gauge is being used, place the gauge where
it can easily read, yet not in the way. If an aneroid gauge is being used,
attach it to the bladder.

j. Position Patient's Limb.

(1) If the bladder is to be applied to the patient's upper arm and there is a
support for the patient's arm (bed, table, ground, etc.), have the patient to
extend his arm in a palm up position. The arm should be about the same
level as his heart.

(2) If the bladder is to be applied to the patient's upper arm but there is no
support for his arm, tuck his wrist under your arm so that you will be
supporting his arm and keeping it steady.
(3) If the bladder is to be applied to the patient's thigh, the patient should
remain lying on his abdomen or lying on his back with his knee flexed.

k. Wrap Bladder Around Limb.

(1) If the upper arm is being used, wrap the bladder around the upper arm.
The non-slip material or buckles of the bladder should be on the outside of
the bladder, not next to the patient's skin. The bottom edge of the bladder
should be one to two inches above the elbow (figure 5-6).

(2) If the thigh is being used, wrap the bladder around the middle of the
thigh (figure 5-7). A somewhat larger and longer bladder is normally used
when the blood pressure is taken in the thigh.

Figure 6. Placement of bladder on upper arm.

Figure 7. Placement of bladder on thigh.

(3) Wrap the bladder firmly around the limb. Overlap the fabric and make
sure it will not slip (Velcro to Velcro, fasten buckles, tuck fabric end under
(4) If an aneroid gauge is being used, wrap the bladder so that the gauge is
aligned with the palm of the hand if the arm is used and with the kneecap
if the thigh is used. Positioning the gauge in this manner will make it easier
for you to read the dial.

l. Locate Pulse. Put the earpieces of the stethoscope in your ears (plastic tips
forward) and use the diaphragm to find the patient's pulse.

(1) If the upper arm is being used, you will use the brachial pulse found
just below the crease on the inside of the elbow (figure 5-8).

Figure 8. Locating brachial pulse.
A Side view. B Top view

(2) If the thigh is being used, use the popliteal pulse just above the crease
on the inside of the knee.

(3) If you are using a combination stethoscope (both disk and bell) and you
cannot hear anything, find the lever near the diaphragm and flip it. This
will change the source of sound input from the bell to the disk.

m. Tighten Screw. Make sure that the valve is completely closed so that the
air cannot escape.

n. Inflate the Bladder. Inflate the bladder (figure 5-9) by squeezing and
releasing the handbulb. Listen to the patient's pulse and watch the gauge as
you pump up the bladder. When you can no longer hear the pulse beat,
note the reading on the gauge. Then pump the handbulb again until it
reads 10 mm Hg higher than it did when the pulse disappeared or until the
pressure of 140 mm Hg is reached, whichever is greater.

Figure 9. Inflating the bladder.

CAUTION: Do not inflate the bladder to a pressure greater than 200 mm
Hg. If the pulse can still be heard at 200 mm Hg, deflate the bladder
(unscrew the valve) and remove the bladder from around the patient's arm
or thigh. Then notify your supervisor of the problem

o. Listen for Pulse. Once you have inflated the bladder to the desired
pressure (140 mm Hg or higher, depending upon when the pulse
disappeared) listen briefly to make sure that you cannot hear the pulse beat

(1) If you cannot hear the pulse, then the air pressure inside the bladder is
greater than the systolic pressure of the blood. (The bladder is, in effect,
now a tourniquet.) You are now ready to begin releasing the air from the

(2) If the pulse can still be heard, inflate the bladder until the pulse
disappears, then inflate it an extra 10 mm Hg of pressure. Do not inflate
above 200 mm Hg.

p. Release Air Slowly. Watch the gauge closely and listen through the
stethoscope as you release air from the bladder. Air is released from the
bladder by rotating the release valve (screw) counterclockwise (figure 5-
10). The more the screw is turned, the larger the opening and the faster the
air escapes. You want the air to escape slowly enough so that you can tell at
what pressure reading the pulse reappears, but fast enough that the
continued pressure does not harm the patient or cause unnecessary
discomfort.

Figure 10. Rotating the screw counterclockwise to release pressure.

(1) The process of taking a patient's blood pressure (beginning at the time
you start inflating the bladder and ending at the time you completely
release the pressure) should take less than two minutes. Do not leave an
inflated bladder wrapped around the patient's limb for more than two
minutes.

(2) If you are having problems that will result in going over the two minute
mark, deflate the bladder, remove the bladder from around the patient's
limb, and wait at least one minute before trying to take his blood pressure
again.

q. Listen for Pulse. The point at which you hear the pulse beat return is the
patient's systolic pressure. Note the reading on the gauge when you hear
the first distinct sound of a pulse beat.
(1) The markings on the gauge will mark off readings (130, 132, 134, etc.).
When you record blood pressure readings, record the reading to the
nearest even number (for example, 128 instead of 127).

(2) Normally, you will remember the patient's systolic reading and not
write it down until you have the determined his diastolic reading also.
Writing the number down distracts you from listening to the pulse and
watching the gauge as the air continues to escape.

r. Continue to Release Pressure. After you identify the patient's systolic
pressure, continue to listen to the pulse and watch the gauge as the air
continues to escape from the valve. The air should be escaping at a rate that
does not require you to adjust the airflow (turn the screw).

s. Listen for Last Distinct Sound. As long as the air pressure in the bladder
is greater than the diastolic pressure, the artery will collapse after each
pulse beat. This makes the pulse have distinct sound. Once the air pressure
in the bladder is less than the diastolic pressure of the blood, the artery will
remain open at all times. This means that you will be hearing the sound of
continuous blood flow in addition to the blood surge caused by the pulse.
The pulse will sound muffled and not distinct. The point at which the
distinct pulse sound changes to a muffled sound marks the diastolic
pressure.

(1) Often the pulse will sound louder just before the diastolic pressure is
reached.

(2) A change in rhythm may also occur at the diastolic level.

(3) Sometimes the diastolic is difficult to determine. You may wish to close
the valve (turn screw clockwise), inflate the bladder to a point where the
pressure is above the diastolic, and release the air at a slower rate than
before in order to check yourself.

(4) Like the systolic, the diastolic is determined to the nearest even whole
mm Hg.
t. Release Air. Once you have determined the patient's diastolic pressure,
rotate the screw counterclockwise until the valve is opened as far as
possible. This will allow the bladder to deflate rapidly.

u. Verify Readings, if Needed. If you are not sure that the blood pressure
readings (both systolic and diastolic) are correct, squeeze all the air out of
the bladder while it is still wrapped around the patient's arm and repeat
steps m through t. The blood pressure can usually be checked quickly
because you already know the patient's approximate blood pressure
readings. This means that you will usually inflate the bladder quickly to a
pressure about 10 mm Hg above the first reading, release the air slowly
until the first pulse is heard, release air little faster, and then slow the air
flow down when you approach the level of the diastolic reading. If the
second set of readings is very different from the first, remove the bladder
from the patient's limb, force the remaining air out, wait one minute, and
take his blood pressure again.

v. Record Readings. Record the systolic and diastolic readings. The systolic
is written first and is separated from the diastolic by a diagonal line. For
example, a systolic of 120 and a diastolic of 80 is written "120/80." Both
reading are recorded as whole, even numbers.

w. Remove Bladder. Remove the bladder from around the patient's arm or
thigh, force the remaining air out of the bladder, and close the valve.

x. Assist Patient, If Needed. Assist the patient as needed. For example, you
may need to help the patient with his shirt or pajamas.

y. Clean Earpieces. If you are not going to continue using the stethoscope,
clean the earpieces again. Use the same procedures as previously described
in paragraph d.

z. Return Equipment. If you will no longer need the sphygmomanometer
and stethoscope, return them, along with any other equipment used, to
their proper storage area.
CAN I TAKE A PATIENT'S BLOOD PRESSURE WITHOUT A
STETHOSCOPE?

Sometimes the noise level of your work area may make it very difficult to
listen to the patient's pulse with a stethoscope or you may not have a
stethoscope available. In such cases, use your fingertips (not your thumb)
to feel the pulse instead of using a stethoscope to listen for the pulse. The
following steps summarize how this procedure is performed.

a. Position the Patient. Position the patient so that you can easily take the
patient's pulse.

b. Locate Pulse. Locate the patient's pulse (inside elbow or knee).

c. Place and Inflate Bladder. Wrap the bladder around the patient's upper
arm or thigh, as appropriate. (The bladder must be placed between the
pulse site and the patient's heart.)

d. Inflate Bladder to Starting Point. Inflate the bladder while continuing to
feel the patient's pulse. Inflate the bladder until you feel the pulse stop;
then inflate it another 10 mm Hg.

NOTE: Inflate the bladder to at least 140 mm Hg, but not more than 200
mm Hg.)

e. Release the Air Slowly. Turn the valve so that air escapes. Continue to
feel for a pulse and continue to watch the gauge.

f. Determine Systolic. The systolic is the pressure at which you feel the first
pulse beat return.

g. Determine Diastolic. The diastolic is the pressure at which the pulse
changes to a less distinct (more normal) pulse. The diastolic measurement
is only an approximation since it is usually difficult to determine the
diastolic using this method.

h. Release Air. Open the valve fully in order to relieve the pressure as
quickly as possible.
i. Verify Readings, If Needed. If you wish to check your results, squeeze the
air out of the bladder, close the valve, and repeat the procedure.

j. Record Readings. Write the patient's readings (systolic/diastolic) on the
form or paper. Remember that both readings are to be even whole
numbers.

k. Remove Bladder. Remove the bladder from the patient's arm or thigh.
Also assist the patient to adjust his clothing or position as needed.

l. Return Equipment. If you are not going to take another patient's blood
pressure, return the sphygmomanometer to the proper storage area.

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